Tom Brady’s Mouthguard

Watch Tom Brady’s mouthguard. In and out of his mouth it goes, covered in saliva, football sweat, and dirt. Hanging in or out of his helmet. And where else has it been? Common places that football players stash their mouthguards between plays include on the facemask, in socks, on the bench, inside skullcaps, and held in the hand. Not surprisingly, studies reveal that mouthguards are typically covered with all kinds of bacteria, fungi, and yeasts associated with disease and infection. So why doesn’t Brady get sick?

In essence, it’s because as the mouthguard’s microbiome—the organisms that live on its surface—changes with each football field, each helmet, and each insertion, so too does the immune system and the genetic makeup of Tom Brady. Add to all this, the fact that the average lifespan of actual human cells in our body is estimated to be only 4,000 seconds (about an hour). So the Tom Brady you see at the beginning of the Super Bowl is not the Tom Brady raising the trophy or mourning the loss. 

What do I mean by “actual human cells?” Well, it turns out that we are not entirely—or even mostly—human. Of the 10 trillion microorganisms that make up the human microbiome, only 1 in 10 is identified as a human cell. What’s more, only a fraction of our 9 trillion non-human organisms have even been clearly identified as bacteria, virus, prion, or any other living organisms that we understand. We are made mainly of organisms that we have yet to understand.

Let me explain. We have known about bacteria since the 1600s and finally made the link between germs and disease in the 1860s and 70s. The first virus was discovered in 1892, while the first prion (a protein that causes progressive neurodegenerative conditions) wasn’t identified until the 1960s. These discoveries have been enormously helpful in medicine. However, 20% of the DNA in your nose and 40-50% of the DNA in your gut codes for organisms we have not yet identified: so-called “biological dark matter.” This large amount of unknown genetic coding and whatever organisms they imply make up most of what we consider ourselves to be.

Not only that. The ecosystem of the human body is constantly being invaded, and the immune system responds to these known and unknown invaders with varying strength and effectiveness. While a small portion of the response may be preprogrammed by your genetic makeup, the reality is that there are too many new and unknown organisms to keep up with. Fortunately, we have a response system that modifies itself by recording each new invader (memory cells) and modifies our genes themselves so they can produce a range of proteins and other molecules to defend our bodies in the future.

This, of course, brings up the current crisis of COVID-19 and its constantly evolving variants. While these diseases are getting appropriate attention, be confident of the human response to the virus. We are evolving and developing novel immune responses to each attack. We also have the benefit of new vaccines, which jumpstart the body’s normal defensive response to invader variation in our favor. And the more people who are vaccinated, the fewer hosts there are for viruses to use as manufacturing facilities.

Tom Brady doesn’t often get sick, despite the presence of all kinds of nasty things in his mouthguard, because of the flexibility of his response system and the natural turnover of cells in the setting of an otherwise healthy human body. You too can avoid getting sick by being vaccinated, reducing exposure during the outbreak (masking and distance), and maintaining a vigorously healthy body to defend against the blitzing invaders.

Originally published on January 24, 2015. Updated on February 7, 2021 by Kevin R. Stone, MD.